Method of making coated paper moisture resistant



R. J. GRIMM Nov. ll,- 1952 MFII'RX) OFIMAKING COATED PAPER MOISTURERESISTANT- Filed llarGh 8, 1952 Am. Bussum:

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Patented Nov. 11, 1952 METHOD OF MAKING COATED PAPER MOISTURE RESISTANTRichard J. Grimm, Whitesboro, N. Y., assignor to St. Regis PaperCompany, New York, N. Y., a corporation of New York Application March 8,1952, SerialNo. 275,605 I 3 Claims. (Cl. 117-64) f This `inventionrelates to methods for manu-- facturing moisture resistant paper, theinvention beingparticularly adapted, among other possibilities, for theproduction of relatively vinexpensivel coated paperV adapted for highspeed lithographic printing. `In lithographie printing the plate rollsused are ordinarily kept in clean condition by aqueous mixtures, withthe consequence that small amounts of moisture, along with the ink, arecarried onto thepaper duringprinting.y .With this method of printing,particularly if coated paper is used and is 'travelling at a high speed(for example800900 feet per minute) such moisture is suicient to causeparticles of the coating to be released anddisplaced or picked off, thusseriously interfering with good quality printing, unless the papercoating is in somewaymade moisture-resistant. f L

To. providev such moisture-resistance, it has heretofore been commonpractice to coatr the paper off the machine, that is, as a separateoperation after .the paper leaves the papermaking machine. In such casescasein-claycoating mixtures have been commonly used incorporating aningredient such as formaldehyde which has the property of renderingwater lresistant such ,adhesives asl casein. Since with suchoff-the-machine coating,

. thespeedlof the paper during 'the coating operationiis lrelativelyslow, the coating composition usedpmay comprise a quite thinmixture'thatis, a mixture of'lovv viscosity and having a high watercontent, and hence sufficient amounts offormaldehyde solution may beincorporated 'therein with-V out causing the coating mixture to hardenbefore itis properly applied or distributed on the paper as acoating.yHoweventhis method of producing a moisture-resistant paper for thepurpose -has the disadvantage that the coatingA of `the paper relativelyslowly as an operation separate from the manufacture'of paper, involvesa substantial extra. expense` as compared with the cost of modernhigh-speed methods of coating paper on thepaper making machine.Accordingly elforts haveheretofore been made to provide some way bywhich paper could be coated on the paper making machine, or Without anextra handling operation, to provide a product sufcientlymoisture-resistant for high-speed lithographie printing purposes,` andwith avoidance of the extra cost of off-the-machine coating which mayamount to 50% or more. To this end attempts have beenmade to incorporatein the coating mixture on the paper making machinevmaterials such asformaldehyde or other ingredients for Cil 2' rendering the coatingmoisture-prooff However, since coating paper at the necessary lhighspeeds :on the machine requires the useof a mixture having a high solidscontent so that it will quickly dry, it has been found that attempts tointroduce formaldehyde into such a mixture caused the .coating materialto more or less solidify so rapidly that it could not be properlyapplied and uniformly distributed on the paper as a coating. Attempts'touse other chemicals for the purpose during coating on the paper machinehave not, so'ffaras is known, met with any substantial commercialsuccess, for various reasons. z y

yOther attempts tosolve the problem have in volvedcoating the paper onthe machine and lthen the application ofa Waterproong agent such asformaldehyde'in aqueous solution to the coated paper as it passes overthe calender at thefend of the paper machine. Still other attemptshave'involved the application of formaldehyde as agas to the paperafter. coating. These attempts also', so farr as is known, have not metwith anysubstantial commercial success and involve difficulties ofsecuring uniform treatment throughout the surface of the paper, and alsovthe very serious difficulty that formaldehyde, as an obnoxious gas,escapes into the room to such a serious extent that it cannot betolerated by theworkmen.

According tothe present invention, paper vis coated by known methodspreferably at high speed on the paper making machine by applying theretoknown or conventional"`coating mixtures embodying a pigment such as clayanda proteinaceo'us adhesive such as casein (or a proteinaceous adhesiveVsuch as isolated soya protein as commonly used in paper coatingmixtures), and then as the paper leaves the dryer rolls of thev papermaking machine and is about to pass through the machine calender stack,or later as itk isabout to be passed through the usual supercalenderfitis treated with formaldehyde by incorporating the formaldehyde in theso-called steam showers,-

such as are customarily used for applying steam to the paper onsupercalenders. the preferred method, an aqueous solution containing forexample from ILO-40% of formaldehyde) is allowed to drip vinto the hotinteriorn'of the steam shower enclosure so that formaldehyde gas isentrained in the streams of steam whichv are projected throughsmallexhaust apertures onto the paper just as the paper is to pass betweenthe rolls of the calender.

serve forcefully to apply `the formaldehyde, caus- According Vto Thusthe customary steam showers which are used to softenl the paper and thecoating vthereon at the calender,`

ing it effectively to penetrate the web surface and impart the desiredmoisture-proof characteristics to the adhesive thereof, and since theapplication of the formaldehyde in this way is immediately followed bythe compressing and smoothing of' the paper between the calender rolls,the method has the effect inf-insuring thoroughpenetrati'onof L theadhesive by the formaldehyde and the'prn'pt locking, in eiect, of theformaldehyde into the surface of the web. At the same time it has beenfound that this method of projectingthe formal-wdehyde as embodied inexpanding jets of steamY-f onto the paper is surprisingly effective inpreventing objectionable escape of the obnoxious gas'into"-"-f theatmosphere of the room. Other and more specic objects, features andadvantages of the invention will vappear Hfrorn'the if detaileddescription given below, taken in con-.- nection with the accompanyingdrawings which"A form a part of this specification and illustrate bywayef 'example' one formA ofV equipment whichmay' be usedin carryingout'the invention('Th'einventionconsist's in such novelu features andI'come binatioiffs'of features as may be hereinafter more specificallypointed'out and specified `in the'ape' pen'dedcl'aimsf. l

In the? drawings :i

Fig." '15 is a side view; somewhatdiagrammatic,' l of a"siip'ercale'nder equipped 'and'arrange'd with steainshowers 'andassociated special equipment"` for"'carryin`gout the inventionin thepreferred way;""""

Fig. 2 is an enlarged transverse sectional 'vievvff through 'one'of the'Msteam showers'showing 'the preferred'means by Vwhich'the formaldehydeAmay Fig' isalOngitddinal sectional'viewoi por'-V reference" character'S, 'and "others "having fiber' surfacesl of conventional type'asindicated by the referencecharacter F. "So-called y rvolls-'areindicated at 20,' 2|` etc. for guiding thevpaper'as' J it emerges 'from'between the nip of adjacent rolls,

into the -neir'tnip of the rolls.'r The paper' maybe? fed as from aroll"22 onto the' top roll ofthe calender' and thence' down' Ythroughy'the' calender ontof'a powerldriven' wind-up roll 23 of conven-`tionaf'drm.

35 running to waste, whereas the remaining steam passes up aroundbetween the walls of cylinders 32 and 34 to either a slot or a series ofapertures B positioned along the top of the cylinder 34, and along aline transverse to the moving web closely adjacent thereto, sothat a jetor jets of steam' :3T frcefu-llyiimpingelponithe Ylpipferfweb. In r'dei"t`o"'embdy the`f'frmaldelyde"in the steam jet or jets 31, preferably atank as at 4D is provided, connected by piping as at 4I to a pipe 42extending-longitudinally of the space between thefcylinders'f' and 32.The lower side of pipe 42 is provided either with spaced apertures or aseries 4'of sprayers-'as 'at-42' (Fig. 3) permitting liquid'tobe'sprayedo'l'it at a rate subject to regulationas 'lierei'naft'erdescribed ontothe exterior of the'pipe or `cj'fli'nder 3U'- which is being maintainedin heated condition by the presence of the steain"An aqueous 1040%solution of the formaldehyde may be used in thetank 40. However. the'percenta'g'-'f the 'solutirmaybe 'fvaie'd-f Withinf'wide-limits'-- 'i' ly n Y At least'i the' fm'ajor part-lof th r-r''a'ld'ely'dsolutionisprayeid'onto tlie'fheated'fit' ioifo Y 'th pip'efo'rcylinderf-a' is vapri'z'e'df'fandthorelglily- 'mixed with and carriedalong by the steam1 throu'g-lthe orifice' or'apertii'e 736,'

St'en" 'showers`"are indicated at '2li 'and 25 for applying steam"V tothe' opposite surfaces ie' spectiviyo'f the paper. It wiube noted'thareach' t0 thturfac 0f the paper which is about t0 b engagedlrsuccessivelyby a plurality of 's'teel'rolle'rs' which'act toiron out and polish thepaper surface'.

That is, theV steam'shower 24 ispositionedto apply steam to that'surface of the paper. which is to be engaged by the steel rollers l0and I2, andthe As indicated in Fig. 2, the'fo'rm of steain'show'er"means `here used'may-comprise central steam'inlet pipess, '39 extendingtransversely of the moving I' webaiid'having a slot or' a series' ofapertures at 3i forpermitting the steam to escape" into an 32 aidfihtoan outer' cylinder'34. 'Condensatie g drains'from the latter cylinderthrough 'aconduit otherwise.

snrfac'e"eitherl by reason of dissolving'the 'g' sjin theiine'particles' 'of vresulting condensatef'ior The draining ofcondensate 'fronithe'bbaomr Y cf the.' vste'arnshowers throughpipe'slasat 35 'jv will insure that the steam it passes @through f then'ricesat36 will be substantiallyv dry'ahdfreeof droplets ci waterwhichwouldim'part a` non-uniform treatment tothe web. 'At the' sa'm timeany excess@formaldehyde solution 'which is' not substantiallyvaporized'and jentraiii'ed'rin the" escaping stearnrwi11r te drained'away through'- both thesteam and formaldehydetreatments onl the webwill be uniform. f A i It lwillloe apparent that theiinvention may beapplied to the treatment of paper board as well as-paper and other Webs,coated or uncoated, and which embody adhesives capable of being'ren'-4dered moisture resistant by the action of formaldehyde.' Y

ment lfor carrying out this method is small, since equipment essentiallycomprises the available calenders or supercalenders and accompanyingsteam showers. While it is believed not to be essential that any specialVentilating equipment `l() It will be apparentthat the expense forequip- Y or hoods be provided for confining or carrying aWay escapingvapor, if desired the upper surface of each steam shower may be providedwith baille plates or walls as at 45, 46 interconnected at their ends byproperly shaped end pieces so as to provideg'a chamber 41, the top ofwhich is substantially closed by the moving web. This structure willitend to conne the steam and vapor for somewhat more effective treatmentof the paper.v

QWhiIe the method is preferably carried out during the supercalenderingoperation where,`

steam shower facilities are usually already availm able, it will beapparent that similar steam' showers might be applied to the usualcalender at the end of the paper making machine (which,` t of course,follows the usual dryer rolls of th e riiachine) to permit the use ofthe invention atv that point if preferred, or in cases where supericalendering of the web may be unnecessary.

r The temperature and amount of the steam used Highly satisfac-j doesnot appear to be critical. tory results have been obtained using steamvshowers the same as customarily used in supercalendering coated paper.For example the steam entering the cylinder may be at a tem-.

perature in the neighborhood of 255 F. and at a pressure of 60 lbs. Theamount of formaldehyde in solution used is also not critical, althoughit is desirable that enough be used so that continuous sprays thereofwill be directed onto the cyl-'- inder or pipe 30. As above indicated,the percientage of formaldehyde used in the solution may also be variedwithin wide limits as only a small quantity is necessary in treating thecoated paper for the above-indicated purposes, and any excess will bedrained away inthe condensate passing out through pipes 35. The coatedpaper treated in accordance with this invention has been found topresent a highly satisfactory surface with improved gloss for high speedlithographie printing, particularly for multi-colored printing. Onesuitable form of regulating apparatus for supplying the formaldehydesolution will now be described in connection with the enlarged Viewvthereof shown in Fig. 2 and a View thereof on a smaller scale in Fig 1.The commercially avail-7' able formaldehyde solution may be supplied asin a barrel 54, which is subjected to air pressure as by compressed airconnection 5|, the solution passing from the barrel through a shut-offvalve ,'52 and a pipe 53, preferably having a check valve ,as at 54 at apoint prior to its entry into the tank 48. Within or adjacent the tank40 a ing valve 55 of suitable known type may be provided for mixing thesolution with a desired pro,-v portion of water coming in through awater supply line 56 and a check valve 51. The mixing valve may also beof a suitable oat controlled` type controlled in a known way as by afloat 58S`- in the tank40 and arranged so that whenever formaldehydesolution, but whenthe tank 4U is filled toa predetermined level, theVmixing valve will shut off the supplies of both the water and:solution. VThe tank 40 is also preferably con# nected to an air pressureline as at 60 entering' through a pressure regulating valveV 6I having avent pipe `62 which will'be opened by the pressure regulating valvewhenever the pressure in the tank 48 is greater than the pressure', assupplied by pipe 60 regulated by valve 6l. The barrel 50, for example,may be subject to a pressure of 30v lbs. per square inch, Whereas thetank 40 may normally be subjected to a pressure, for example, of 20 lbs.per square inch. 'I'hus when the mix-i ing valve 55 is opened by theiioat, the tank 40 will be subjected to pressure from the barrel higlienough to allow the mixed liquids to enter, and suicient air or vaporabove the liquid in the tank 48 will escape through the vent 62 to allowthe liquid level to rise to the desired predetermined point ascontrolled by the float.

The piping 4| for carrying the solution into the steam showerspreferably is provided With a soleheid-operated shut-oil` valve 65 andthe steam pipe 36 may also be provided with a similar valve 55, boththese solenoid valves preferably being operable by the same circuit asindicated in Fig. i and arranged so that when the electric current isshut off, the flow of both solution and steam to the showers will be cutoff.

As indicated in Fig. 1, the solution and steam may be carried to theshower 24 by branch pipe i lines Illa and 36a respectively, which areconnected to the piping 4l and the steam pipe 30.

While in the interests of economy in the u 'se of formaldehyde, somespecial means is desirable for mixing the commercially availableformaldehyde solution with water and for regulating the supply of themixture properly under pressure, means other than that shown may, ofcourse, be used such as mixing tanks from which the solution ows bygravity into the steam showers.

This application is a continuation-in-part of application Serial No.143,185, filed February 9, 1950, now abandoned.

While the invention has been described in detail with respect toparticular preferred examples, it will be understood by those skilled inthe art after understanding the invention, that various changes may bemade and equivalents may be used without departing from` the spirit andscope of the invention,

What is claimed as new and desired to be secured by Letters Patent is:

l` In the calendering of a dried paper web which has been coated on thepaper making machine with a mixture embodying clay and wwwwhi'ehhais-beenfcoatedwith a; mixture embodying: clayind'fsoywproteinfadhesive, the .method of providingftheidred'webWitha'rnoisture-resistant glossyi'print ifeceptive fsurface suitable for`high 1 5 speedV l"lithog'lfampl'iic-' printing; which comprises facfhasbeen effectively` calendered:

clayfand an-fadhesiversel tedfjjrom ,thegroup j; oonsis'tingrof easeingandsoyafprotein. the method Y of lprovidirrfithe-#driedfwebl *with a.moisture-fw; resistant glossy print receptive-surfamefsuitable` forhighfspeed iitho'graphic printingi'whichfcom-i prisesforming-an,intimateintermixture'of 'steamandformaldehyde,iimpinging*said'mixture onto a.. f coated' fac'o'ftheidied coated-'Web and imrnedi-' ately: subjeting'thethusi'treate'd'face of the web v' vto the ironing action of calenderrolls until such facet has` been 'eiectively" c'alendered:

RICHARDfmGRn/LMA f

3. IN THE CALENDERING OF A DRIED PAPER WEB WHICH HAS BEEN COATED WITH AMIXTURE EMBODYING CLAY AND AN ADHESIVE SELECTED FROM THE GROUPCONSISTING OF CASEIN AND SOYA PROTEIN, THE METHOD OF PROVIDING THE DRIEDWEB WITH A MOISTURERESISTANT GLOSSY PRINT RECEPTIVE SURFACE SUITABLE FORHIGH SPEED LITHOGRAPHIC PRINTING, WHICH COMPRISES FORMING AN INTIMATEINTERMIXTURE OF STEAM AND FORMALDEHYDE, IMPINGING SAID MIXTURE ONTO ACOATED FACE OF THE DRIED COATED WEB AND IMMEDIATELY SUBJECTING THE THUSTREATED FACE OF THE WEB TO THE IRONING ACTION OF CALENDER ROLLS UNTILSUCH FACE HAS BEEN EFFECTIVELY CALENDERED.